The Vienna regional court has given Facebook four weeks to respond to a 25,000 plaintiff class-action lawsuit over privacy.

The lawsuit, called “Facebook v Europe”, is being led by privacy campaigner Max Schrem, who saw overwhelming support for his case from people wanting to back his suit. It was approved by the regional court in Vienna on Thursday.

The court ruled that Facebook must respond to the suit within four weeks or the judge can rule without it. Facebook can apply for an extension.

“The first step in the legal procedure is hereby taken,” the class-action group said in a statement. “If Facebook Ireland refuses to submit a counterstatement the court would be able to make a judgment in absence based on the lawsuit.”

“So far more than 25,000 Facebook users from outside of the US and Canada have assigned their claims to join the class action, in what has become the largest privacy class action in Europe overnight,” continued the group adding that an additional 35,000 users had registered through its class-action claim site despite the lawsuit being capped at 25,000 plaintiffs.

Fighting in Ireland

Schrems is claiming damages of €500 (£397) per plaintiff for alleged data protection violations by Facebook, including its alleged participation in the US Prism spy programme. The action is targeted at Facebook’s Irish subsidiary, where the social network’s European operations are based.

The Irish Data Protection Commission already has 20 active complaints from Schrems over alleged data breaches including reuse of data without a users’ effective consent and unauthorised transmission of data to third-party applications.

Facebook is facing a similar landmark battle in Ireland, which was referred to the European court of justice by a judge in Dublin last month, to find out what Facebook tells US spy chiefs.

Facebook has more than 1.3 billion users. Its shares are trading on the Nasdaq at around $72, making it worth in the region of $200bn (£118 billion).